Oops
by MasterHyperion-Reborn
Summary: A slip-up, and Severus Snape realises he doesn't really know Harry Potter. After witnessing the impossible, and almost losing the last thing he'll protect with his life, he'll resolve never to underestimate a Gryffindor again. Rated M for some bad language.


**A/N**

**Disclaimer: I do not own Harry Potter. JK Rowling does. Anything you recognise is hers. Anything you don't, well, I'm laying claim to that. Or, you know, it could just be JK's stuff you forgot abut. Like Emmeline Vance. Or maybe you remember her. I certainly didn't until I got into the FanFics.**

**Hi there guys! I was just about to try and finish the next chapter of Mors Ulnas, when I had some inspiration. If you recognise this concept, sorry about that, but I'm sorta sure that it came from a story I read a while ago, but I can't for the life of me remember what it's called, or I'd have referenced it. Sorry! Anyone think it's theirs, or know who wrote a similar story, please tell me in a review or something. Enjoy!**

Severus Snape scowled out at his class. While this was not entirely unusual, the cause of it was: Potter had succeeded where the entire of the rest of the class had failed, and had made a _perfect_ potion. Not only this, but he had managed this while clearly tired and distracted, and almost constantly rubbing his left hand while he was at it.

When he had seen this… Odd behaviour, his first instinct had been to bear down on him and demand an explanation for not only the blatant inattention in _his_ lesson, and then remove whatever charm or hex had been placed on his hand to make it itch so much, if only so he could gloat about the boy having missed it. Then he realised he could have a lot more fun. He could force Potter to drink the concoction, of course first ascertaining it wouldn't kill him, in front of the class and _then_ ridicule him for his hand, before sending him, of course begrudgingly, to Poppy to be sorted out.

After another hour, at which point the potion was supposed to be done, he surveyed the class, and quickly saw that most people had completely failed. Hardly surprising, as this was far above even seventh-year work, being closer to what apprentices would create in their preparation in the final year of a mastery. Some did catch his eye, though. Granger had done passably well, and would most likely scrape an Acceptable for it. Of course, Snape admitted to himself with chagrin, it was truly appropriate for an Outstanding, especially as they were only in Fifth Year. Draco's attempt was only slightly worse, but Zabini's potion was even better, and would no doubt be troublesome for Longbottom, the person he had Severus had decided to inflict Zabini's attempt on. The others were all dismal, and would produce no effects, or, in the case of Crabbe, Goyle and Longbottom, would doubtless have exploded if Severus hadn't been especially vigilant today, as the potion was known to be especially volatile if done incorrectly.

Severus scanned the final people as they all cleared away their spare ingredients and books. None caught his eye, until he reached Potter's potion… Potter.

How had he done this?! He was fifteen years old, for Merlin's sake!

Wait, no. It must be a mistake – he couldn't have done this correctly. He double-checked Potter's potion, searching for something, _anything_ wrong with it. No. Potter had somehow succeeded in creating a perfect potion that wasn't even taught in Hogwarts, but in fact in the last year of a _4 year_ Mastery course!

_How?!_

Nothing else to do, he supposed, except call for them to come up with all reasonably successful attempts, and find out what Potter was like without any inhibitions.

"All those who think they have managed to complete this potion to a reasonable degree, come to the front. Their lucky partners are to join them once handing in their own sorry attempts. Any who haven't succeeded in even doing that, leave the vials on my desk, labelled with your name, for me to peruse at my displeasure."

As the class bottled up their attempts of drastically varying success, Severus saw, out of the corner of his eye, as Potter seemed to snap out of whatever daze he had been in before he spoke, and seemed to look in a sort of confused, wary way around him, and then towards the potion in front of him. At that point a look of panic and fear washed over him, before suddenly disappearing, to be replaced with a look of complete indifference. Severus then saw the boy go to 'accidentally' knock his potion off the table. He obviously didn't realise what the potion would do if it came into contact with the floor at high velocity, and Severus knew he had to act quickly…

Harry was woken by a voice that certainly wasn't Ron's, nor did it belong to anyone else in his dorm. It was the baritone voice of Severus Snape, telling him to… _come to the front?_ What was going?

As he became more awake, he realised he wasn't in his bed, but what appeared to be the Potions Classroom. This in itself presented a problem, as he definitely didn't want a potion made while he was at least half asleep paraded in front of the class. The Gryffindors were fine, but Merlin help him if Dra-Malfoy saw what he'd done.

Come to think of it, what had he made? He looked at the board at the front, and the name at the top: _The Non Mentiens Potion_. Harry was both surprised and mildly amused. On the one hand, it was quite surprising he hadn't blown up, asleep as he was. On the other, it was just like Snape to give them a potion reserved for Mastery apprentices.

_Well, no reason in delaying, I suppose. How bad is it?_ With only mild trepidation, now he knew the difficulty of the potion set, he looked down, and froze. Fear forced its way into his mind, along with shock. _How in Merlin's name had he done that? He could he, half asleep, perfectly make a potion he had only managed last week? _He looked around, and realised that people were making their way u to the desk, some, the failed, depositing theirs on Snape's desk, while Zabini, D-Malfoy and Hermione were standing in front of the man himself, with Neville, Ron and Seamus nearby. _What could he do?_ The answer came quickly enough, and with it, his mask slipped back, despite him not realising it had cracked.

He stood up, and feigning clumsiness, knocked his cauldron off the desk in front of him, and started stepping swiftly back, in preparation for the explosion that would no doubt severely injure him, but hopefully no kill him…

He also spoke, only one quiet word, that doubtless very few people heard, but he really didn't want Snape to notice this before it was too late.

"Oops."

It appeared, however, that Snape had seen his less than subtle move, as before the cauldron tipped onto the floor, it was caught in a stasis charm designed exactly for such an occurrence.

_Well, fuck._

As a number of vials flew up, Harry realised he'd not only done it perfectly, but in the same quantities as last week, i.e. an entire cauldron-full. About 15 full-power doses. _Shit. Shit. Shit. Shitty fecking ARSE!_

With nothing to do but accept it, Harry followed the floating batch up, perfectly aware of the shocked gazes of the entire class on him. _Again_.

Once he reached the front of the class, he was prepared for whatever comment Snape might make. To his surprise though, Snape said nothing, simply placed fourteen of the vials on his desk, separate to the rest, and floated the final one to Harry's waiting hand.

Severus found a migraine coming on. Not only had Potter created a perfect potion, but he had also done it in industrial size amounts.

Deciding hat it could wait, he first turned to Granger, who was still gaping at Potter.

"Ms Granger, stop allowing flies free lodging in your mouth and give your attempt to Mr Weasley to drink."

Her mouth snapped shut, only to open again almost immediately.

"Yes sir."

She handed it to Weasley, who hesitantly raised the potion to his lips, and drank the concoction down.

The _Non Mentiens_ potion had some very interesting effects. Its first is to remove all magical changes to the drinker's body – Metamorphs, Glamours, transfigurations, Animagus forms, even Polyjuice.

The second, however, is far more interesting. It removes all inhibitions from a person. Well, more accurately, it makes a person unable to factor fears, insecurities and morals into their judgement. This can be quite… Interesting. Which is why Severus was so curious to see what would happen to Potter. If it were done only slightly incorrectly, the effects were lessened, and Severus was looking forward to seeing Weasley embarrass himself.

"Mr Weasley, what do you think of me?"

"I think you're a greasy-haired, dungeon dwelling... Bat."

As predicted, the idiot wasn't dosed up to lose complete control.

"Yes, well, you're going to have to clean these dungeons in which I dwell for a week's detention." I could tell he was about to complain, and most likely say something worse. Remarkably, I felt, given I'd forced him into this, that was far enough.

"No points have been lost because you refrained from swearing in my face." At this point, a combination of this and Granger's frantic elbowing forced Weasley to stop, and, moments later, he was out from the limited potion's effects.

"Now, Mr Finnigan. Drink."

Finnigan glared openly at Zabini as he collected his dose. That alone made Severus think this would be especially amusing. Such little survival instinct even before drinking…

"Now, Mr Finnigan," he said, allowing a smirk to creep slowly across his face as he spoke, "What do you think of me?"

"I think you're a foul, cruel, petty man who has no place in a school."

And Severus was right again. He let out a bark of laughter in his mind. His face, on the other hand, was contorted into a snarl.

"Detention for the next month, Mr Finnigan, and 50 points from Gryffindor!"

Finnigan went to speak again, but Granger's hand clamped over his mouth, and the effects soon subsided.

"Next. Mr Longbottom, collect your dose from Mr Malfoy."

Longbottom, hands shaking, nervously took the proffered vial and drank.

"Now, what do think of me?"

"I try not to."

"But when you _do_" Severus ground out. He wasn't used to his question being evaded in such a way…

"I think of how much I would enjoy torturing you until you broke." At the class' shocked expression, and even Severus' broken mask, he smirked, "along with your little friend Bellatrix."

Severus resolved there and then that he would need to be more careful when choosing his victims. Always the quiet ones…

"Finally, Mr Potter, given you seemed to be unable to stay awake in my lesson," Here Granger gasped, and glared at Potter. Stupid girl, far too trusting in authority. "You are to drink your own potion."

Potter hesitated; clearly desperately thinking of a way out of his situation. "Now, Mr Potter." With a final glare at Severus, he closed his eyes, and drank the entire bottle. Severus' mask broke yet again to stare. How had Potter hidden this?!

All over his arms and neck were scars. Just below the short-sleeve robes they all wore during the summer, a massive wound, from what appeared to be a snake bite, showed, a dark red, much darker than the other scars. On his left hand, clear to Severus and the others lingering at the front, but not the rest of the class, as it was the hand holding the vial; still near his face, the words 'I must not tell lies' was carved into the flesh. There was the reason he had been rubbing it while in whatever daze he had found himself in. Suddenly he realised the changes weren't done. Slowly, before everyone's eyes, his body shifted, becoming taller, leaner, and yet… More defined. More shocking was his visible skin. It had changed colour, becoming golden, gleaming in the little light there was in the dungeon. His hair had lost the black colouring it was famed for, lengthening and turning a pure, shocking white. His face lengthened, becoming, like his body, leaner, sharper. Not even his eyes were spared. Gone were the soft, bright green eyes of Lily Evans. In their stead, pure black eyes, with no white visible, stared out of the completely unknown man's face.

The transformation over, Harry Potter gazed out at the class, his face set in a decidedly Slytherin smirk.

Why had he been so worried about this? So his glamours were gone, he didn't even need them, really. They were there as a safeguard should his Metamorph abilities fail him. Most people don't think to get rid of both.

Now, he could do what he wanted. Without his pesky little worries getting in the way… He needed the rest of that potion. His friends needed release. They needed to be ready to fight with him.

Getting over his shock – _after all, who didn't hide themselves?_ Severus decided to just continue. It was best if he simply kept the boy occupied until the potion wore off. No doubt trouble with the Headmaster would come from this, but… He could deal with that later.

"Now you've finished your little show, Potter, what do you think of me?"

"I have immense respect for you." Once again, the entire class was shocked, staring at him in shock, even Granger, who, despite that, still managed to look mildly approving of Potter respecting him… Potter respected him. Him! Severus Snape! Severus couldn't even comprehend the concept of a Potter respecting someone. Although, he didn't even look like a Potter anymore…

"Yes," Potter continued, looking at Severus' amazed face with open amusement, "not many people could, in the same day, kneel at the feet of the Dark Lord Voldemort, torture a muggle family, doubtless not _merely_ with the Cruciatus, but physically. Was Tom in a particularly good mood?" Severus was having trouble processing what he was hearing. Potter really kept a lot hidden. "Not only this, but you then managed to _lie to his face_, and then immediately go to Dumbledore, in whose face you _also lie_, and _then_ come down here and force a load of fifth years to brew an exceedingly dangerous Mastery level spell just so you could take some points from Gryffindor. It's really quite impressive." Here his smirk widened into a grin: "I mean, not even _I_ managed all that!" Another pause, his time as he rearranged his face into a thoughtful expression, "Just the first four."

This broke the spell. Potter had knelt at The Dark Lord's feet? He'd tortured muggles? Granger spoke at this point, obviously unable to hold it in anymore

"Harry! You don't know what you're saying!" Weasley obviously felt the need to pile on.

"She's right Harry! You're under the effects of a potion!"

"Oh get a room! Merlin! You'd think, between you, you'd have realised your feelings, right? WELL APPARENTLY NOT!" The two others of the Golden Trio quailed under his eyes. Suddenly, Potter got a gleam in his eyes, one that frankly terrified Severus, especially as his face morphed slightly, becoming very reminiscent of Black. "On the subject of relationships…" He said with another smirk, turning away, towards the main class.

At this Severus had to intervene. Potter was having an extremely unpredictable reaction to the potion, but he would still eventually be out from its influence. And, as much as he resented the boy for Lily, he still had a vow to keep. Reaching out to take hold of Potter's arms, he spoke, this time without his customary sneer,

"Potter, while going to say hello to the Weasley girl may seem like a very good idea at the moment, the effects of this potion will fade very soon, and you will regret it, if you do this now." Potter simply removed his arm from Severus' grip.

"Whoever said it was Ginny?"

Suddenly, with a speed Severus would have thought impossible for anyone, Potter crossed the classroom, towards… The Slytherins?

He walked straight up to Draco, and mashed his lips against the other boy in an almost desperate movement.

**A/N**

**Well, this was fun. I'll probably do another chapter for this soon, but this seemed a good place to stop for now. As I said at the top, this was just a random thought. Anyways, yes, conclusion soon, and I'll get back on Mors Ulnas soon.**

**-MasterHyperion-Reborn**


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